1. Field of the Invention
This invention relates generally to reticulated sheet material, commonly referred to as grating, and more particularly, to a method and apparatus for fabricating such reticulated sheet material.
2. Description of the Prior Art
Grating is well known, and can be categorized into two basic types. One type is essentially a stamping formed by a set of dies that impart a three-dimensional contour and usually drainage holes into a sheet of mechanically workable material. The basic limitation of this type is that the depth of the grid is usually limited, thus limiting the strength of the structure.
The other type is a reticular network grid material similar in configuration to the structure described in U.S. Pat. Nos. 2,828,792 and 2,828,843. A characteristic of the reticular network grid is that the grid can be formed with relatively deep members. Thus, steps and other supports fabricated from such a grid structure are thus quite strong and suitable for industrial pedestrian traffic.
While a reticular network grid is a stronger structure than a stamping, the presently available reticular grids exhibit several inherent deficiencies caused by the fabricating apparatus and the method of fabrication. Firstly, most grids exhibit irregularly shaped openings that are usually asymmetrical in configuration. The strands that form the opening are commonly tipped so that the center line of the opening deviates from its intended vertical orientation, and the strands usually do not reach a uniform level. Excessive tearing at the interconnections between the strands is common, as is a nonuniformity in the shape of the ridges that interconnect the strands. In addition, the currently used method and apparatus for fabricating the grid structures puts an undue strain on the material being worked, thus requiring the use of relatively thin materials with easy cold working characteristics, and limits the sizes of openings and grid pattern shapes that may be achieved without causing undue strain on the material during the fabrication process.